Elements

[StrandedonEarth]

1 minute ago, fredinno said:

It should actually be left of Hydrogen, as it has an atomic number of 0

Oh, right. So the periodic table should start with neutronium and end with unobtainium.

[GeneralVeers]

Yeah.....uhh, folks? Buzzkill incoming: neutronium can't be considered an element for purposes of this thread, because SuperFastJellyfish asked what stable elements can exist.

That's the thing with neutronium. When outside of an atomic nucleus, neutrons are highly unstable at standard temperature and pressure. If you could somehow grab a spoonful of neutronium from a neutron star, it would explode!

Sorry, sci-fi wonks. You can't make a starship hull out of this stuff.

[SuperFastJellyfish]

I'm okay with this thread derailing.    My questions have been answered(thanks, all).  Speak freely!  Well, keep it on an elemental basis, anyways. 

Edited March 17, 2016 by SuperFastJellyfish
Clarity

[lajoswinkler]

1 hour ago, fredinno said:

That's not an element at all!

It should actually be left of Hydrogen, as it has an atomic number of 0. 

Well, you can have a Neutron with an electron orbiting it- it will decay in 15 minutes, but it seems to resemble an atom in every other way except by not having a proton https://en.m.wikipedia.org/wiki/Neutronium

Neutron can not be orbited by an electron, at least we never saw that happening. Lone neutron has a halflife of ten minutes.

[fredinno]

23 minutes ago, GeneralVeers said:

Yeah.....uhh, folks? Buzzkill incoming: neutronium can't be considered an element for purposes of this thread, because SuperFastJellyfish asked what stable elements can exist.

That's the thing with neutronium. When outside of an atomic nucleus, neutrons are highly unstable at standard temperature and pressure. If you could somehow grab a spoonful of neutronium from a neutron star, it would explode!

Sorry, sci-fi wonks. You can't make a starship hull out of this stuff.

 Francium would also explode, and that's still an element.

[cantab]

1 hour ago, insert_name said:

I heard that the last possible element was one that had its electrons so far out they were orbiting at relativistic speeds, not sure how big it would be, but the nuclear forces would be immense

In a non-relativistic model, element 137 would have outer electrons orbiting faster than light. It is I believe not a coincidence that 137 is approximately 1/alpha , the fine structure constant. Of course relativity does applied, and already with the transactinide elements it is thought to have an effect on the chemistry. For example element 118 is in the noble gases group but some predictions are that it is actually quite reactive.

18 minutes ago, GeneralVeers said:

Yeah.....uhh, folks? Buzzkill incoming: neutronium can't be considered an element for purposes of this thread, because SuperFastJellyfish asked what stable elements can exist.

That's the thing with neutronium. When outside of an atomic nucleus, neutrons are highly unstable at standard temperature and pressure. If you could somehow grab a spoonful of neutronium from a neutron star, it would explode!

Sorry, sci-fi wonks. You can't make a starship hull out of this stuff.

A piece of a neutron star would explode due to nuclear forces repelling the neutrons apart, with the sudden removal of gravity that was confiding them. But a lone neutron has a half life of 15 minutes. Compared to most of the transactinide elements humans have synthesised, that's AGES.

[fredinno]

7 minutes ago, cantab said:

In a non-relativistic model, element 137 would have outer electrons orbiting faster than light. It is I believe not a coincidence that 137 is approximately 1/alpha , the fine structure constant. Of course relativity does applied, and already with the transactinide elements it is thought to have an effect on the chemistry. For example element 118 is in the noble gases group but some predictions are that it is actually quite reactive.

A piece of a neutron star would explode due to nuclear forces repelling the neutrons apart, with the sudden removal of gravity that was confiding them. But a lone neutron has a half life of 15 minutes. Compared to most of the transactinide elements humans have synthesised, that's AGES.

Actually, it's the innermost electron shell that'd be going at FTL speeds (higher gravity well), and it's debatable whether it's actually 137 or 173 in which that happens.

[GeneralVeers]

2 hours ago, fredinno said:

 Francium would also explode, and that's still an element.

Just because a thing that is an element also explodes, does not mean all things that explode are elements.

 

2 hours ago, cantab said:

A piece of a neutron star would explode due to nuclear forces repelling the neutrons apart, with the sudden removal of gravity that was confiding them. But a lone neutron has a half life of 15 minutes. Compared to most of the transactinide elements humans have synthesised, that's AGES.

Probably both forces would contribute to a kaboom. Fredinno mentioned the element francium up above; francium has a longer half-life than free neutrons (22 minutes for the most stable isotope) and any sample of francium large enough to be visible to the naked eye would be instantly melted and vaporized by its own heat of decay. Yeah, 15-22 minutes is a long time, but the small fraction that decays immediately produces enough energy for an explosion. Not an explosion on the same scale as a nuclear bomb, though I suppose with a big enough chunk of neutron star confined in a forcefield, you could make a pretty nasty superweapon.......

[GoSlash27]

My guess:
 We are already familiar with every stable element in the universe. There simply aren't any more.

This is assuming that the physical constants are uniform everywhere.

Best,
-Slashy

[sevenperforce]

19 hours ago, fredinno said:

You can have a Neutron with an electron orbiting it- it will decay in 15 minutes, but it seems to resemble an atom in every other way except by not having a proton https://en.m.wikipedia.org/wiki/Neutronium

Either I am REALLY missing something, or that's not actually a thing. There's nothing to keep an electron orbiting a neutron. An electron in orbit around a neutron is a bound state but there are no conservative fields to enable additional mass to be contained within that bound state.

Neutronium is sort of a slang term for any state or phase or arrangement of matter consisting primarily of neutrons. It's mainly used in reference to neutron-degenerate matter under gravitational compression and Pauli exclusion pressure, but it can also be used for metastable neutron pairs, triplets, and so forth in temporary strong-force attraction.

18 hours ago, cantab said:

19 hours ago, GeneralVeers said:

When outside of an atomic nucleus, neutrons are highly unstable at standard temperature and pressure. If you could somehow grab a spoonful of neutronium from a neutron star, it would explode!

A piece of a neutron star would explode due to nuclear forces repelling the neutrons apart, with the sudden removal of gravity that was confiding them. But a lone neutron has a half life of 15 minutes. Compared to most of the transactinide elements humans have synthesised, that's AGES.

Strictly speaking, a sample of neutron-degenerate matter would explode due to quantum forces. The stuff at the surface of the neutron star is held in place by the strong force, which attracts; gravity also ensures that it remains on the surface. As you go deeper, though, the weight of the stuff above you increases until the nuclear strong force no longer matters, because the weight of gravity is holding the nucleons together even more tightly than the nuclear strong force can.

The density increases as the nucleons are squeezed more and more tightly together, until finally quantum spin characteristics (Pauli exclusion principle) prevent them from merging entirely. This is an incredibly high amount of force; gravity squeezes them together against this outward force and thus stores tremendous potential energy in that quantum field.

If you removed a sample of NDM from the gravitational field holding it together, the energy stored in the quantum field would be released instantly, and that is what would make it explode.

[GeneralVeers]

8 hours ago, GoSlash27 said:

My guess:
 We are already familiar with every stable element in the universe. There simply aren't any more.

Easter egg from some Star Trek Voyager episode, the name of which I don't remember.

One of the science wonks on the Voyager crew is trying to solve "The Problem" (which I also don't remember) and is searching the periodic table. If you watch close, on the computer screen, you can see an element with atomic number 483.

That's a lotta protons........

 

2 hours ago, sevenperforce said:

Strictly speaking, a sample of neutron-degenerate matter would explode due to quantum forces.

And I thought it was convoluted when there were only two competing theories--now there's three.

Headache not improving.

[sevenperforce]

2 minutes ago, GeneralVeers said:

Easter egg from some Star Trek Voyager episode, the name of which I don't remember.

One of the science wonks on the Voyager crew is trying to solve "The Problem" (which I also don't remember) and is searching the periodic table. If you watch close, on the computer screen, you can see an element with atomic number 483.

That's a lotta protons........

Haha! Totally impossible. No way to have a stable nucleon matrix of that size.

Nucleus stability is a little like the variety of regular convex 3-symmetric polyhedrons. Tetrahedrons are simple. Cubes are simple. Icosidodecahedrons are a little more complicated. The more faces you add, the more types of faces you'll have to add, and eventually it becomes less and less possible to make it work. Same thing with nucleons; as you try to pack them into a tight sphere, the ones at the surface keep getting less and less firmly affixed.

6 minutes ago, GeneralVeers said:

And I thought it was convoluted when there were only two competing theories--now there's three.

Headache not improving.

They're not competing theories....

[GeneralVeers]

Uhh.......yeah, when one guy says "strictly speaking, X would happen instead" that's competing.

[Bill Phil]

19 minutes ago, sevenperforce said:

Haha! Totally impossible. No way to have a stable nucleon matrix of that size.

Nucleus stability is a little like the variety of regular convex 3-symmetric polyhedrons. Tetrahedrons are simple. Cubes are simple. Icosidodecahedrons are a little more complicated. The more faces you add, the more types of faces you'll have to add, and eventually it becomes less and less possible to make it work. Same thing with nucleons; as you try to pack them into a tight sphere, the ones at the surface keep getting less and less firmly affixed.

They're not competing theories....

It's Star Trek though. They probablt found some new type of particle that can stabilize higher proton count numbers. Technobabble, basically.

[sevenperforce]

30 minutes ago, GeneralVeers said:

Uhh.......yeah, when one guy says "strictly speaking, X would happen instead" that's competing.

More correcting than competing....

**stops being a jerk**

Okay, sorry.

[fredinno]

20 hours ago, GeneralVeers said:

Just because a thing that is an element also explodes, does not mean all things that explode are elements.

 

Probably both forces would contribute to a kaboom. Fredinno mentioned the element francium up above; francium has a longer half-life than free neutrons (22 minutes for the most stable isotope) and any sample of francium large enough to be visible to the naked eye would be instantly melted and vaporized by its own heat of decay. Yeah, 15-22 minutes is a long time, but the small fraction that decays immediately produces enough energy for an explosion. Not an explosion on the same scale as a nuclear bomb, though I suppose with a big enough chunk of neutron star confined in a forcefield, you could make a pretty nasty superweapon.......

How would you contain it? Neutrons don't interact in charges...

[cantab]

1 hour ago, fredinno said:

How would you contain it? Neutrons don't interact in charges...

Fixions.

 

[GeneralVeers]

1 hour ago, fredinno said:

How would you contain it? Neutrons don't interact in charges...

That was me dabbling in sci-fi. I did use the word "forcefield"...... (actually, such things aren't entirely fictional.....)

My evil plan: confine a charge of neutron star matter at stable density, using a forcefield or whatever, transport the charge to where you want it, then drop the forcefield. The charge becomes unstable. Huge kaboom. With the added bonus of the explosion consisting of a large amount of actual matter which exerts a lot more force than a nuclear blast wave.

(I mourn the demise of the Evil Superweapons thread......)

[fredinno]

18 hours ago, GeneralVeers said:

That was me dabbling in sci-fi. I did use the word "forcefield"...... (actually, such things aren't entirely fictional.....)

My evil plan: confine a charge of neutron star matter at stable density, using a forcefield or whatever, transport the charge to where you want it, then drop the forcefield. The charge becomes unstable. Huge kaboom. With the added bonus of the explosion consisting of a large amount of actual matter which exerts a lot more force than a nuclear blast wave.

(I mourn the demise of the Evil Superweapons thread......)

Getting off the Neutron Star Gravity well kills this idea. You need to go at 1/3 the speed of light to escape neutron stars.

[GeneralVeers]

I think human science will one day reach a point where that's actually doable.

[GoSlash27]

On 3/18/2016 at 2:53 PM, GeneralVeers said:

Easter egg from some Star Trek Voyager episode, the name of which I don't remember.

One of the science wonks on the Voyager crew is trying to solve "The Problem" (which I also don't remember) and is searching the periodic table. If you watch close, on the computer screen, you can see an element with atomic number 483.

That's a lotta protons........

Emphasis on "stable".

 Who knows how many elements could temporarily exist before they're ripped apart from their own internal forces? But stable elements is a different question. If we assume that the physical constants are uniform throughout the universe (and our observations tend to support this notion), then there simply aren't any more. A nucleus can only get so massive before it spontaneously breaks down into lighter elements.

Best,
-Slashy

[GeneralVeers]

1 hour ago, GoSlash27 said:

Emphasis on "stable".

Heheh. Yeah. It was Star Trek; they simply hand-waved the minor fact that element 483 is probably unstable as heck.

Is there any hard evidence at all for the "island of stability", or is it hypothetical?

(from what I've read of it, it's more an "island of relative stabiliity" whose elements merely last longer before going kablooey)

[GoSlash27]

1 minute ago, GeneralVeers said:

Heheh. Yeah. It was Star Trek; they simply hand-waved the minor fact that element 483 is probably unstable as heck.

Is there any hard evidence at all for the "island of stability", or is it hypothetical?

(from what I've read of it, it's more an "island of relative stabiliity" whose elements merely last longer before going kablooey)

GeneralVeers,

 I'm far from an expert in these matters, but everything I've seen on the subject agrees with this.

 The island of stability is a projection of the behavior of large atoms based on what we currently know, and it has proven accurate so far.

Best,
-Slashy

[sevenperforce]

11 hours ago, fredinno said:

Getting off the Neutron Star Gravity well kills this idea. You need to go at 1/3 the speed of light to escape neutron stars.

Well, if he has a forcefield capable of containing quantum neutron degeneracy pressure, it ought to be trivial for him to open up one end of said forcefield and create a rocket with a specific impulse of three million seconds. 

5 hours ago, GeneralVeers said:

Heheh. Yeah. It was Star Trek; they simply hand-waved the minor fact that element 483 is probably unstable as heck.

Is there any hard evidence at all for the "island of stability", or is it hypothetical?

(from what I've read of it, it's more an "island of relative stabiliity" whose elements merely last longer before going kablooey)

Simulations suggest that there is a small set of proton+neutron combinations a little larger then unbiseptium which have half-lives of minutes-to-days. The simulations are consistent with what we have currently created, but we haven't gotten any further than unbiseptium (118 IIRC) so far. 

[cantab]

118 is ununoctium. unbiseptium would be ... 127 I think?